One embodiment of the present invention relates generally to an automatic play device such as a sequencer of a musical instrument, automatic accompaniment device, automatic rhythm playing device or the like, and more particularly to an automatic play device which can effectively realize a smooth tempo change from one tempo to another corresponding to a tempo change operation.
In Japanese Patent Laid-open Publication Nos. 58-211191 or 63-193192, there is disclosed an example of a sequencer-type automatic play device of which stores play data inputted from a keyboard of a musical instrument, a computer or the like and reproduces a tone based on the stored play data. In such an automatic play device, the play data is read out from a memory in response to a tempo clock, and then a tone signal is generated based on the read-out play data. The tempo clock frequency can be changeably controlled in correspondence to a tempo setting value and thus the reproduction play tempo can be freely changed to desired one. The tempo setting value can be continuously changed by operating a tempo setting knob, or it can be changed in response to a suitable switch operation. However, the prior art automatic play devices are disadvantageous in that when tempo change operation is made during the play by means of the tempo setting operator such as the knob or switch, the tempo is caused to change immediately and hence abruptly to a new tempo after the operation, which inevitably gives an impression of awkward intermission. Further, in such device that can continuously change the play tempo by the operation of the tempo setting knob, it will become quite an obstacle to turn the knob slowly during a manual play in an order to change the tempo smoothly.
Also, the aforesaid sequencers can be connected via MIDI terminals with a MIDI musical instrument, and the automatic play tempo can be adjusted by changing a tempo clock frequency of play data supplied from the sequencer to the MIDI musical instrument connected in master-slave fashion therewith. In a specific type of the sequencers, the tempo can be changed in correspondence to the player's own beating time action; for example, in the case where a pedal switch for adjusting a tempo is provided in the sequencer, the player can control the automatic play tempo by stepping on the pedal switch at a desired tempo (hereinafter, this step-on operation will be called a tap). In this case, the sequencer detects when the pedal switch is stepped on (switched on), and at each time of detection, it changes a timing clock frequency in accordance with the time interval between the times of the current and last step-on operations of the pedal switch. However, in such sequencer, since the play tempo is determined in correspondence to the tap interval, the music play is undesirably caused to stop if the player stops tapping. Thus, the sequencer is not satisfactory in that the player must continue to tap for every beat. Also, it is substantially impossible to carry out ritardando, accelerando or the like since the tap tempo change tends to cause the timing clock to abruptly change in uncontinuous manner, which results in unnaturality of music.